U.S. Republican presidential candidates stand on stage prior to the start of their debate on national security at the Daughters of the American Revolution Constitution Hall in Washington, D.C., on November 22.

The eight candidates from the Republican Party who hope to defeat U.S. President Barack Obama in November next year all agree on one thing.

They all accuse Obama of failing to deal adequately with three key foreign-policy challenges to the United States: Afghanistan, Pakistan, and Iran.

But when it comes to the details of what they would do, big differences emerge. And it was those differences that dominated the Republican candidates' debate in Washington D.C. on November 22.

The debate, hosted by CNN and two conservative Washington think tanks, took place just blocks from the White House and before an audience largely made up of foreign-policy experts.

During the two-hour session, the candidates -- few of whom have significant foreign-policy experience -- broke from their usual debate of domestic issues to speak about the U.S. place in the world.

Gingrich: 'Cut Off Iran's Gas'

The leading candidate at the moment is former U.S. House of Representatives Speaker Newt Gingrich, who took a lead role in revitalizing the Republican Party in the 1990s and hopes to do so again now.

Former Speaker of the House Newt Gingrich

Gingrich charged Obama with weakness in pursuing U.S. goals in Afghanistan and Pakistan and promised a tougher approach.

"You want to keep American troops in Afghanistan?" Gingrich asked. "You accept hot pursuit, you say no sanctuaries, you change the rules of engagement, you put the military in charge of the military side, you overhaul the State Department and AID [Agency for International Development] so they get the job done and you do it for real and you do it intensely and you tell the Pakistanis: 'Help us or get out of the way, but don't complain if we kill people you're not willing to go after on your territory where you have been protecting them.'"

Gingrich similarly faulted Obama for taking too soft an approach with Iran. Where Obama has first sought to engage, and then sanction Tehran, Gingrich called peaceful regime change the better strategy.

He said that "if we were serious, we could break the Iranian regime" within a year, starting with "cutting off the gasoline supply to Iran and then, frankly, sabotaging the only refinery they have." Gingrich's approach appears based on the fact fuel shortages in Iran have previously prompted popular protests against the government.

The former U.S. House speaker called a peaceful change of government in Iran preferable to a war or military strikes, and said the United States should bomb Iran's facilities to prevent it from becoming a nuclear power only "as a last recourse."

Romney: 'Bring Pakistan Into 21st Century'

Another candidate, former Massachusetts Governor Mitt Romney, who has frequently topped the candidates' popularity ratings in the past, also took a firm line on Afghanistan and Pakistan. But he chose softer words.

Mitt Romney (left) and Rick Perry shake hands after a debate in September.

Charging Obama with wanting to leave Afghanistan early, he said he would follow the advice of U.S. military commanders and keep troops there to deter the nation from again becoming a terrorist safe haven.

And he called Pakistan in need of urgent development. "We need to bring Pakistan into the 21st century, or the 20th century for that matter, so that they can engage throughout the world with trade with modernity."

On Iran, Romney called for isolating the regime through "crippling economic sanctions," cooperation with Israel, and a stronger aircraft-carrier presence in the region. He said crippling sanctions would make gasoline more expensive but "there's no price which is worth an Iranian nuclear weapon."

Perry: 'Sanction Iran's Central Bank'

Most of the other candidates, too, charged Obama with laxity toward Islamabad and Tehran -- the two foreign capitals that came up most frequently in the debate.

Governor Rick Perry, once a chief rival for the front-runner position, vowed to cut off aid to Pakistan until it cooperates more with Washington.

"They've showed us time after time that they can't be trusted and until Pakistan clearly shows that they have America's best interests in mind, I would not send them one penny," Perry said.

Perry also vowed to step up sanctions on Iran. Addressing another candidate in the debate, he said: "We need to sanction the Iranian Central Bank. That would be one of the most powerful ways to impact that and as a matter of fact, Congressman [Ron] Paul, [what] we need to do before we start having any conversations about a military strike is to use every sanction that we have.

"And when you sanction the Iranian Central Bank, that will shut down that economy. At that particular point in time, they truly have to deal with the United States."

Paul: 'Mind Our Own Business'

Two of the remaining five candidates in the debate have also been past leaders in popularity polls before seeing the ratings drop in the campaign so far. They are U.S. Representative Michele Bachmann, the only woman in the race, and Herman Cain, the only former business executive.

Bachmann broke with the leading candidates to take a softer stand on Pakistan, calling it a nuclear state Washington cannot afford to see fail.

"At this point I would continue that aid [U.S. aid to Pakistan] but I do think the Obama policy of keeping your fingers crossed is not working in Pakistan and I also think that Pakistan as a nation is kind of like too nuclear to fail."

Cain underlined his concern over Iran's nuclear program by saying he would support Israel if it had a "credible plan" to attack Iran.

The three candidates in the field who have yet to enjoy a stint at the top of the pack sought to use the debate to reignite their campaigns.

Representative Ron Paul -- a consistent antiwar voice -- called for an end to U.S. military adventures overseas. Calling for a more modest foreign policy that he said would make the United States less of a target for attacks, he asked, "Why don't we mind our own business?"

Former Governor Jon Huntsman Jr., said, "Our interests in the Middle East is Israel and preventing Iran from going nuclear."

And former Senator Rick Santorum said Pakistan's nuclear weapons made it imperative that it remains a U.S. friend.

The debate was the 11th of the Republicans' presidential campaign so far, as the party looks to its first formal nomination contest in January.

The nomination contests, which will take place state-by-state through the course of next year, will end with just one candidate representing the party in the November 2012 presidential election.